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Comparison of Microbial Communities in a Simulated Chloraminated Drinking Water Distribution System Subjected to Episodes of Nitrification
Citation:
Revetta, R., C. Bennett-Stamper, D. King, K. Schrantz, S. Pfaller, J. Pressman, D. Wahman, AND V. Gomez-Alvarez. Comparison of Microbial Communities in a Simulated Chloraminated Drinking Water Distribution System Subjected to Episodes of Nitrification. Presented at American Society for Microbiology, New Orleans, LA, May 30 - June 02, 2015.
Impact/Purpose:
These results provide an ecological insight into the succession of microbial communities in chloraminated drinking water systems. Metagenomic approaches used in this study wll help to develop a more comprehensive understanding of the microbial ecology of drinking water distribution systems. Such information is critical to the design of effective management practices and ultimately helps to prevent waterborne disease and safeguard human health.
Description:
Bacterial populations were examined in a simulated chloraminated drinking water distribution system. After six months of continuous operation, coupons were incubated in CDC reactors receiving water from the simulated system to study biofilm development. The study was organized into five distinct operational schemes: (1) PRE-MODIFIED; system stabilization, (2) STANDARD I; stable chloramine residual, (3) FAILURE; complete nitrification and minimal chloramine residual, (4) RESTORE; chlorine burn, and (5) STANDARD II; stable chloramine residual. Bulk water and biofilm samples were collected and analyzed for water quality parameters and community composition. No change in biomass (protein and ATP assays) in bulk water and biofilm samples was detected during the STANDARD I scheme, while an increase in biofilms was detected after 80 days (FAILURE, i.e. nitrification) followed by a decrease after a chlorine burn with a final increase to previous values (STANDARD I) during the STANDARD II scheme. The estimated populations of heterotrophs (HPC) were constant for all samples. Approximately 68% of the viable (PMA treated) microbial community (Illumina 16S rRNA) total diversity was associated with the class Alphaproteobacteria, Actinobacteria, and Gammaproteobacteria with additional contributions (<29%) from 109 classes. Ordination plots (nMDS and PCA) and one-way ANOSIM tests showed clustering of samples and significant differences in functional (PICRUSt analysis and shotgun metagenome) and community (16S OTUs) structures based on source (e.g. disinfection treatment), surface material and operational schemes. For example, members of the family Methylobacteriaceae (22%) dominated chlorine-treated water (i.e. municipal water), while early stages of operation (PRE-MODIFIED) were dominated by Novosphingobium (38%). Environmental Mycobacterium-like OTUs peaked during the STANDARD I scheme (40%) but decreased to <10% in later periods, and an increase in the abundance of nitrifying bacteria Nitrospira (<0.3% to 4%) was observed during the FAILURE scheme. In addition, ammonia-oxidizing bacteria (qPCR) related to Nitrosomonas were detected during nitrification. These results provide an ecological insight into the succession of microbial communities in chloramined drinking water systems.
